WP_Block_Pattern_Categories_Registry The main instance.
	 */
	public static function get_instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}

		return self::$instance;
	}
}

/**
 * Registers a new pattern category.
 *
 * @since 5.5.0
 *
 * @param string $category_name       Pattern category name including namespace.
 * @param array  $category_properties List of properties for the block pattern.
 *                                    See WP_Block_Pattern_Categories_Registry::register() for
 *                                    accepted arguments.
 * @return bool True if the pattern category was registered with success and false otherwise.
 */
function register_block_pattern_category( $category_name, $category_properties ) {
	return WP_Block_Pattern_Categories_Registry::get_instance()->register( $category_name, $category_properties );
}

/**
 * Unregisters a pattern category.
 *
 * @since 5.5.0
 *
 * @param string $category_name Pattern category name including namespace.
 * @return bool True if the pattern category was unregistered with success and false otherwise.
 */
function unregister_block_pattern_category( $category_name ) {
	return WP_Block_Pattern_Categories_Registry::get_instance()->unregister( $category_name );
}
<br />
<b>Fatal error</b>:  Uncaught Error: Call to undefined function register_block_pattern_category() in /home/valigeria/public_html/wp-includes/block-patterns.php:39
Stack trace:
#0 /home/valigeria/public_html/wp-includes/class-wp-hook.php(324): _register_core_block_patterns_and_categories('')
#1 /home/valigeria/public_html/wp-includes/class-wp-hook.php(348): WP_Hook-&gt;apply_filters(NULL, Array)
#2 /home/valigeria/public_html/wp-includes/plugin.php(517): WP_Hook-&gt;do_action(Array)
#3 /home/valigeria/public_html/wp-settings.php(695): do_action('init')
#4 /home/valigeria/public_html/wp-config.php(111): require_once('/home/valigeria...')
#5 /home/valigeria/public_html/wp-load.php(50): require_once('/home/valigeria...')
#6 /home/valigeria/public_html/wp-blog-header.php(13): require_once('/home/valigeria...')
#7 /home/valigeria/public_html/index.php(17): require('/home/valigeria...')
#8 {main}
  thrown in <b>/home/valigeria/public_html/wp-includes/block-patterns.php</b> on line <b>39</b><br />